Apparatus for dimensional testing of nominally cylindrical workpieces

ABSTRACT

This invention provides a testing apparatus for nominally cylindrical workpieces enabling errors of both form and concentricity of a workpiece to be assessed, independently of workpiece diameter, while also checking the diameter itself. The workpiece is rotated about a longitudinal axis through at least 180* and two adjustable feelers are maintained in contact with diametrically opposite points on the surface of the workpiece, one feeler being carried by one arm of a forked support while the other feeler is carried by an block capable of lateral displacement relative to the other fork arm, both the forked support and the block being displaceable linearly in a lateral direction by virtue of ligament supports. A transducer responsive to workpiece diameter is carried by the forked support and bears against a reference point in the ligament support for the block which does not exhibit any lateral shifting upon change in workpiece diameter.

United States Patent Zucco APPARATUS FOR DIMENSIONAL TESTING OFNOMINALLY CYLINDRICAL WORKPIECES [75] Inventor: Matteo Zucco, Turin,Italy 73 Assignee: F111? 5551,11." Per Az iiiiu T111111, n11;

[22] Filed: May 25, 1972 [21] Appl. No.: 256,854

[30] Foreign Application Priority Data May 28, 1971 Italy", 68817 A/7l[52] US. Cl. 33/174 Q [51] Int. Cl. G0lb 5/08, GOlb 5/20 [58] Field ofSearch 33/174 Q [56] References Cited UNITED STATES PATENTS 2,547,7194/1951 Rosser 33/174 Q 2,240,184 4/1941 Hathaway 33/147 N FOREIGNPATENTS OR APPLICATIONS 615,024 1/1961 Italy 33/174 Q PrimaryExaminerRobert B. Hull Assistant ExaminerRichard R. Stearns Attorney,Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak ABSTRACT Thisinvention provides a testing apparatus for nominally cylindricalworkpieces enabling errors of both form and concentricity of a workpieceto be assessed, independently of workpiece diameter, while also checkingthe diameter itself. The workpiece is rotated about a longitudinal axisthrough at least 180 and two adjustable feelers are maintained incontact with diametrically opposite points on the surface of theworkpiece, one feeler being carried by one arm of a forked support whiletheother feeler is carried by an block capable of lateral displacementrelative to the other fork am, both the forked support and the blockbeing displaceable linearly in a lateral direction by virtue of ligamentsupports. A transducer responsive to workpiece diameter is carried bythe forked support and bears against a reference point in the ligamentsupport for the block which does not exhibit any lateral shifting uponchange in workpiece diameter.

D 1 Claim, 6 Drawing Figures PAIENTEUNAR 5 w SHEET 1 [IF 3 PAIENTED51914 3.195.055

SHEEI 2 OF 3 FIG. 2 A

PATENTED 51974 SHEET 3 [1F 3 FIG. 5

APPARATUS FOR DIMENSIONAL TESTING OF NOMINALLY CYLINDRICAL WORKPIECESBACKGROUND OF THE INVENTION This invention relates to apparatus fordimensional testing of nominally cylindrical workpieces, such as turnedshafts, gears, and the like, with particular reference to the testing ofthe diameter of such workpieces and the registration of errors ofconcentricity and shape. 7

Normally such workpiece testing is carried out with two different testinstruments, entailing two separate positionings of the workpiece to betested upon each instrument, and necessitating two different operators.In this case the accuracy of the two testing operations may often beinfluenced by human error.

It is in any case necessary to have available qualified personnel ableto carry out, with the requisite care and skill, the two separatetesting operations.

An object of the present invention is to avoid these difficulties anddisadvantages by providing an apparatus which allows, with a singlepositioning of a workpiece, testing of the diameter to check that itlies within predetermined limits of tolerance, and simultaneous testingfor errors in concentricity and form, independently of the dimensions ofthe workpiece.

Another object of the invention is to provide an apparatus of theaforesaid type, which ensures constant measuring and checking accuracy,whilst also allowing the use of personnel which are not highly skilledand minimising errors due to the human element.

A further object of the invention is to provide an apparatus of theaforesaid type capable of use in gauges and modulating elements.

Yet another object of the invention is to provide a device of theaforesaid type which is of simple, robust and economic construction,accurate and durable in operation and simple and convenient to use.

SUMMARY OF THE INVENTION According to the invention there is provided anapparatus for testing errors of concentricity and form of a nominallycylindrical workpiece, independently of the workpiece diameter, and forchecking, at the same time, that the diameter of the workpiece is withinpredetermined limits of tolerance, the apparatus comprising supportmeans for the workpiece permitting rotation of the workpiece about alongitudinal axis, an oscillatory forked support supported from a fixedbase by ligaments and permitting lateral displacement of the forkedsupport relative to the fixed base, two adjustable feelers adapted tocome into contact with the outer surface of the workpiece atdiametrically opposed points, one of the said feelers being carried by'one of the arms of the forked support and the other of said feelersbeing carried by an oscillatory block connected by means of ligaments tothe other arm of the forked support, a first transducer, sensitive tothe workpiece diameter, carried by the forked support and co-operatingwith the said oscillatory block, and a second transducer, sensitive toworkpiece eccentricity, carried by a fixed mounting and cooperating witha reference point which is common to the forked support and theoscillatory block and which is so placed as not to be urged in thedirection of the axis of rotation of the workpiece by movements due todepartures of the workpiece diameter from a standard diameter inrelation to the axis of rotation, whereby rotation of the workpiecethrough at least makes it possible to measure at the same time the errorof the workpiece diameter and possible error in concentricity of theworkpiece, the latter error being measured independently of theworkpiece diameter, and means for connecting said transducers to asignal processing instrument for evaluating the signals provided by thetransducers and providing an indication of whether or not said signalsare within acceptable limits.

BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantagesof the invention will be apparent from the following description, givenby way of non-limiting example, with reference to the attached drawings,in which:

FIG. 1 is a diagrammatic and elevation of apparatus according to oneembodiment of the invention for recording the errors in concentricityand form of a workpiece independently of its diameter and forsimultaneously checking that the diameter is within predetermined limitsof tolerance;

FIG. 2 is a diagrammatic-lateral elevation of the apparatus on a reducedscale;

FIGS. 3, 4, 5 are diagrammatic views corresponding to FIG. 1,illustrating the operation of the apparatus in three different cases,and

FIG. 6 is a geometric diagram illustrating one detail of the apparatus.1

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring to thedrawings, reference numeral 1 indicates a nominally cylindricalworkpiece mounted for rotation between two opposed tapered stocks 2,supported by mountings 3. Alternatively, the workpiece 1 could rest uponV shaped notches to allow rotation of the workpiece about itslongitudinal axis.

The apparatus according to the invention comprises a fixed lower baseplate 4 upon which the mountings 3 are supported. An oscillatory forkedsupport 6 rests on the base plate 4 by means of resilient ligaments 5.The

. dimensions of the forked support 6 are such that it embraces theworkpiece 1 to be tested.

The ligaments 5 are formed of spring steel strips, reinforcedintermediate their ends by non-distorting plates which allow flexion ofthe strips only near their points of connection to the plate 4 and thesupport 6. The forked support 6 is therefore connected to the plate 4,in effect, by means of a vertical articulated parallelogram theupstanding sides of which are formed by the said ligaments 5.

A helical spring 8 extends between two anchorages 9, 10 integralrespectively with the fixed base plate 4 and the forked support 6. Thespring 8 biases the forked support 6 towards a predetermined position.One of the. arms 6a of the forked support 6 carries a first feeler 11located at one end of a laterally extending sliding rod lla the axis ofwhich intersects the axis of rotation of the workpiece l. A secondfeeler 12, borne by a similar sliding rod 12a coaxial with the rod 11a,is held in counterposed relation to the first feeler 1 1, in contactwith a diametrically opposite part of the workpiece]. The sliding rod12a is carried by a small oscillatory block 14, connected to the otherarm 6b of the forked support 6. Setscrews 13 in the block 14 and arm 6amake possible the clamping of the feeler rods 11a and 12a in a desiredposition.

The oscillatory block 14 is connected to the arm 6b of the forkedsupport 6 by means of another pair of resilient ligaments 15, similar tothe ligaments which connect the forked support 6 to the fixed plate 4.The block 14 is subject to the action of a helical return spring 16.

Two fixed stops 7 and 17 are arranged to limit the oscillatory strokesof the forked support 6 and the oscillatory block 14 respectively.

On the arm 6b of the forked support 6 there is mounted a fixed bracket18 which carries a first electronic transducer 19 for measuring thediameter of the workpiece 1. The transducer 19 has a sensing tip 19awhich bears against the oscillatory block 14. Another fixed bracket 20,mounted on the lower fixed plate 4, supports a second electronictransducer 21 for measuring the workpiece eccentricity. The transducer21 has a sensing tip 21a which passes through a hole 22 in the bracket18 and bears against one of the ligaments which connect the block 14 tothe arm 6b of the forked support 6.

By means of the apparatus herein described it is possible to measure thediameter and the relative ovality error of the workpiece 1, registeredby the electronic transducer 19, and at the same time to measure theconcentricity error, or eccentricity, of the workpiece by means of thesecond electronic transducer 21.

In order to define the degree of eccentricity and the magnitude of theovality error, it is necessary to cause the workpiece l to rotate aboutthe axis of the stocks 2 (or the axis of the V supports) through anangle of 180, that is, one half-rotation. During this half-rotation thetwo transducers 19, 21 independently provide instantaneous signalsrepresentative of the errors of concentricity and ovality respectively.

The device allows the imposition of tolerance limits. Thus if thedeviations registered by the two transducers 19, 21 with reference totheir respective normal positions, or zero settings, are comprisedwithin predetermined limits, an electronic instrument (not illustrated)connected to the two transducers provides an assenting signal, whilstconversely if these deviations are outside the said predetermined limitsa visual or audible signal is provided indicating that the workpiece isnot up to standard.

In principle it is possible by means of the apparatus to record directlythe eccentricity error with fixed imposition of tolerance limits,independently of the workpiece diameter, thus avoiding zero setting ofthe measuring instrument, in order to compensate for deviations due toerror in the actual diameter of the workpiece. This is a' consequence ofthe fact that the eccentricity error is measured at a point of referenceidentitied by the letter P (FIG. 3), that is, the tip 21a of thetransducer 21, which is not displaced in the direction of the axis ofrotation as a result of any increase or decrease in the diameter of theworkpiece 1. Naturally the instrument has to be set at zero initiallywith the aid of a specimen or standard workpiece.

In FIGS. 3, 4 and 5 there is shown diagrammatically the action of theapparatus when testing a workpiece where: (a) the diameter of theworkpiece corresponds to that of a reference standard (FIG. 3); (b) thediameter is less than that of the standard (FIG. 4) and (c)the diameteris greater than that of the standard (FIG. 5).

Any discrepancy between the workpiece diameter and the standard diameterdoes not affect the reading of the transducer 21 which records theeccentricity since the horizontal distance C between the point P and thenominal centre R (FIG. 3), taken as the centre of the standard diameterD in questionand not to be confused with the axis of rotation of theworkpiece, remains constant. If, as shown in FIG. 4, the workpiece 1 hasa diameter D, which is less than the standard diameter D, then the twofeelers 11, 12 are each displaced a distance E towards the workpiece,equal to half the difference of the diameters (D4) The feeler 11, shownin the drawings to the left of the workpiece 1, approaches the workpieceas the forked support 6 itself moves towards the right, whilst the otherfeeler 12 approaches the workpiece inasmuch as the block 14 moves by anequal amount leftwards.

Now if one considers, as shown in FIG. 6, the articulated parallelogramformed by the ligaments 15, the block 14 and the arm 6b of the forkedsupport, it will be seen that the points of connection A and B of one ofthe ligaments 15 to the block 14 and the arm 6!; respectively move byequal amounts in opposite directions upon relative displacement of theblock 14 and the arm 6b, as illustrated by the positions A, B and A", B"typically occupied by the points A, B upon displacement between theblock 14 and the arm 6b in opposite directions. The position of thecentre of the ligament 15, corresponding to the point P, will remainunchanged. The same thing happens, as shown in FIG. 5, if the diameter Dof the workpiece 1' is greater than the standard, in which case the twofeelers 11 and 12 move outwards by the same distance E. This makes-itpossible to measure the concentricity independently of the diameter ofthe workpiece, without any preventative adjustment of the apparatus.

It will be appreciated that constructional details of practicalembodiments of the invention may be varied widely from that which hasbeen described and illustrated, without nevertheless going beyond thescope of this invention.

I claim:

1. Apparatus for testing errors of concentricity and form of a nominallycylindrical workpiece, independently of the workpiece diameter, and forchecking, at the same time, that the diameter of the workpiece is withinpredetermined limits of tolerance, said apparatus comprising:

a. workpiece support means permitting rotation of the workpiece about alongitudinal axis;

b. a base fixed with respect to said workpiece support means;

0. a forked support;

' d. a first pair of ligaments mounting said forked support on said baseand constituting with the base and the support a first articulatedparallelogram permitting lateral displacement of said forked supportrelative to said base;

e. two adjustable feelers adapted to come into I contact with the outersurface of the workpiece at diametrically opposed points, one of saidfeelers being carried by one of the arms of the forked support;

f. a block carrying the other of said feelers;

g. a second pair of ligaments supporting said block from the other armof said forked support and constituting with the block and the support asecond said mounting means of a reference point which is the centerpoint of one of said second pair of ligaments, and

k. means for connecting said transducers to a'signal processinginstrument for evaluating the signals provided by said transducers andproviding anindication of whether or not said signals are withinacceptable limits.

1. Apparatus for testing errors of concentricity and form of a nominallycylindrical workpiece, independently of the workpiece diameter, and forchecking, at the same time, that the diameter of the workpiece is withinpredetermined limits of tolerance, said apparatus comprising: a.workpiece support means permitting rotation of the workpiece about alongitudinal axis; b. a base fixed with respect to said workpiecesupport means; c. a forked support; d. a first pair of ligamentsmounting said forked support on said base and constituting with the baseand the support a first articulated parallelogram permitting lateraldisplacement of said forked support relative to said base; e. twoadjustable feelers adapted to come into contact with the outer surfaceof the workpiece at diametrically opposed points, one of said feelersbeing carried by one of the arms of the forked support; f. a blockcarrying the other of said feelers; g. a second pair of ligamentssupporting said block from the other arm of said forked support andconstituting with the block and the support a second articulatedparallelogram permitting lateral displacement of the block relative tothe support; h. a first transducer, sensitive to the workpiece diameter,carried by the forked support and providing a signal related to theposition of said block with respect to said forked support; i. mountingmeans fixed relative to said base; j. a second transducer, sensitive toworkpiece eccentricity, carried by said mounting means and providing asignal related to the position with respect to said mounting means of areference point which is the center point of one of said second pair ofligaments, and k. means for connecting said transducers to a signalprocessing instrument for evaluating the signals provided by saidtransducers and providing an indication of whether or not said signalsare within acceptable limits.